Various methods are used for changing the color of human hair. As a general rule, either substantive dyes or oxidation dyes, which are formed by the oxidative coupling of one or more developer components with one another or with one or more coupler components, may be used to color human hair. These coupler and developer components are known as oxidation dye precursors. The colors obtained with oxidation dyes may be referred to as permanent or semipermanent colors. Oxidative lightening methods, in which natural or synthetic dyes in the hair fiber are destroyed by oxidation, causing the color to be removed, may be used for lightening or bleaching.
In order to accelerate the reaction during the oxidation process, oxidative coloring and lightening agents mostly have an alkaline pH, which may be adjusted using alkalizing agents such as alkanol amines, ammonia or inorganic bases. Although ammonia in particular allows for good coloring results, it also presents disadvantages for the user because of its odor and its irritation potential for skin and mucous membranes. For that reason, efforts are intensifying to develop high-performance oxidative coloring and lightening agents that dispense with the use of ammonia.
These agents mostly contain hydrogen peroxide as the oxidizing agent. As hydrogen peroxide is not sufficiently stable in storage in the alkaline pH range, oxidative coloring and/or lightening agents may include two components, which are mixed together immediately before use. The problem posed by this approach is firstly that of homogeneously mixing the two components. This could be solved by means of correspondingly readily miscible components, in particular low-viscosity liquids; however, the application mixture must be sufficiently viscous for it to be easily applied to the hair and not to drip or run off during the contact time. The problem with commercial high-viscosity cream or gel applications is that applying them to the hair is often a laborious and time-consuming process. Additionally, an uneven application can easily lead to inhomogeneous or even patchy coloring or bleaching results. For that reason, there has been no shortage of attempts to develop other presentation forms.
Some alternatives have included applying lower-viscosity coloring or lightening agents to the hair using special applicator systems or applying coloring agents as a foam. Application as a foam, in particular as an aerosol foam, which are foamed by propellant gases when the product is dispensed, is widespread.
A foam application has advantages over gel or cream applications in terms of applying and distributing the color-changing agents on the user's hair. However, these advantages are countered by disadvantages concerning coloring capacity, in particular with regard to color uptake, which is offset either by means of longer contact times during application or by higher dye or lightening agent concentrations in the preparations. A further problem relating to foam application relates to the stabilization of the foams. Foam stability in particular has a major influence on both the performance and the ease of application of the agents. Foam stability is negatively influenced in particular by the presence of large amounts of salts and dyes or dye precursors. The ideal foams provide a solid, stable foam that leaves behind a soft feel and breaks down slowly on the hair. Frequently, however, the dispensed foams have poor stability and rapidly collapse and liquefy, leaving behind a low-viscosity, dripping solution. The foam should also wet the hair thoroughly and break down slowly to allow for a good color uptake.
Therefore, there is still a need for an easy-to-handle presentation form for oxidative hair color-changing agents, such as a permanent hair color agent or hair bleaching agent. This application form should allow a drip-free application and its performance should not be inferior to that of commercial cream or gel applications, in particular with regard to lightening and coloring capacity and fastness properties. The coloring results should be outstanding in terms of intensity, gray coverage and shine, they should have superb care properties and a long life, including in respect of external influences such as hair washing.
Accordingly, the present specification describes methods for using oxidative color-changing agents, in particular for foam application, such that the aforementioned disadvantages can be overcome. In particular, stable color-changing foams should be provided.
Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.